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Thick seams coal mining is important in Russia. Many high-quality coal seams exceed 35 meters (12 feet) in thickness - the normally accepted classification for a thick seam (although this varies in different countries). Some of these thick seams are of key importance in major mining basins. Seam thickness is the most significant factor which is taken into account in mining practice. The increasing strata movement with increasing seam thickness requires not only specialized extraction techniques, but also highly specialized ground control and support methods. This is certainly true of the coal basins where coal seams are gassy and the majority of coal is liable to spontaneous combustion. Coal seams occur at a depth of between 350 and 710 meters (1,150 and 2,330 feet).
Longwall retreating is the primary method of mining at the collieries with more than 98 per cent of the total output. Application of a mining method with the coal face being advanced down the dip is steadily expanding; shortwall pillar extraction with power loaders is being successfully employed.
Coal faces and development headings are equipped with instruments for automatic gas protection and centralized telemonitoring of methane content. Data on gas conditions in development headings which are particularly dangerous from the viewpoint of methane content, and in all coal faces are transmitted to the mine dispatcher's control panel. In order to reduce gas content in mine workings, extensive use is made of preliminary gas drainage of the coal seams, gas drainage of roofs to be caved and also of the goaf.
The main trend in mine transport is towards high-capacity automatic conveyer systems. In underground workings transport of men and materials is by high-capacity electric locomotives; in incline roadways, by ropeways, floor-mounted haulage and up-to-date hoisting installations.
The mining district is usually developed by mine shafts. The mining method is longwall retreating along the strike and down the dip. The mining area is divided into two blocks east and west. In the eastern block the panels are mined down the dip, in the western block, mining takes place along the strike. The faces are 200 meters long and operate along the strike of the seam. Sandstone forms the immediate roof and floor of the seam. Each face is mining a 3.5-meter thick section of coal, and a 0.5 to 0.8 meter thick pillar (band) of coal is left between two panels to form the roof of the lower face.
Each face is equipped with a double-ended drum shearer. The drums are 1.8 meters in diameter and a 0.6-meter web of coal. The leading drum cuts the top section of the face, and the trailing drum cuts the bottom section. Water jets are fitted to the drums for dust suppression. Coal passes along the face on the armored face conveyer to the crusher installed at the main gate end of the conveyer, which reduces the size of the coal before it is delivered to a beam stage loader in the main gate.
The faces are operated on two production shifts and one maintenance shift per day.
Each face is supported by shield supports.
It should be stressed that special attention is paid to underground methane drainage. The methane is pumped through pipes first to the tail gate and then through the mine gate to the upcast shafts and then to the surface, where it is used for heating. Two sensors for continuously monitoring the emission of CH4 are situated in the top panel, one in the main gate, and the other in the tail gate. These are placed 20 meters in front of the face. The control room at the mine's surface automatically monitors and records CH4 emissions throughout the mine.
In coal face and development operations, use is made of current forecasting of the liability to sudden outbursts, that is, establishing dangerous and non-dangerous zones.
All coal faces are equipped with mechanized complexes, comprising power loaders. In underground haulage roadways, use is made of high-capacity belt and apron conveyers. Coal is hoisted to the surface through two skip shafts. Monorails are widely used on levels for transport of materials and equipment to coal faces and development headings. Some of production processes are automatic.
Разработка мощных пластов
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